a blog for Java

class Random Generate random numbers

class Random Generate random numbers

In some applications, the programmer may be required to generate random numbers within a range as in lottery tickets. The range may be zero to some number or between any two numbers.

Java

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importjava.util.Random;

publicclassRangeNumbers2

{

publicstaticvoidmain(Stringargs[])

{

System.out.println("\t\tNumbers 0 to 200");

Random r1=newRandom();

for(inti=0;i<5;i++)

{

intk=r1.nextInt(200);

System.out.print(k+"\t");

}

System.out.println("\n\t\tNumbers within 10 to 30");

intstartRange=10,endRange=30;

for(inti=0;i<5;i++)

{

intoffsetValue=endRange-startRange+1;

intbaseValue=(int)(offsetValue*r1.nextDouble());

intk=baseValue+startRange;

System.out.print(k+"\t");

}

}

}

Random r1 = new Random();
Random r2 = new Random(150);

The Random class constructor is overloaded – one that takes no parameter and the other that takes an integer value (known as seed ). The first object r1 generates different random numbers at different times of execution. The second object r2 with a seed of 150 generates same set of random numbers at different times of execution. Here, the seed value is 150. Different seed values generate different sets. The random numbers with a seed value is useful to test and bug-fix the software; when the same values are fed, the output of the application should be the same. Random numbers are not thread-safe. Programmer should take care of with concurrency problems in a multithreaded environment.

The nextInt() method returns an integer value and similar methods exist, with Random class, like nextDouble(), nextFloat() and nextLong() etc. that returns a double, float and long values.

The nextInt(200) returns an integer value from 0 to 199. To print between any two values, logic included is self explanatory.

Applications of Random Numbers

The importance of random numbers is increasing day-by-day. Some applications are given below.

Applications of games as in dice-ware

Applications of testing software for searching or sorting

Applications of testing with different input values

Applications of encryption to give guarantee for secrecy

The following program uses random() method of Math class to generate random numbers.